If vector A = i - 10j and vector B = 3i - 4j, then find vector A . vector S.

Question

If \(\vec A = \hat{i} - 10\hat{j}\ and\ \vec B = 3\hat{i} - 4\hat{j} \ \text{then}\ \text{find} \ \vec A.\vec S.\) 

Answer 1

\(\vec A = \hat{i} - 10\hat{j}\ ;\vec B = 3\hat{i} - 4\hat{j}\ ;\vec A.\vec B = ?\) 

\(\vec A.\vec B = (\hat{i} - 10\hat{j}).(3\hat{i} - 4\hat{j}) = 3\hat{i}.\hat{i} - 4\hat{i}.\hat{j} - 30\hat{j}.\hat{i} + 40\hat{j}.\hat{i}\)

= 3 - 0 - 0 + 40 = 43